typedef与没有带有C语言中的结构和枚举的typedef

Question

In C, is there any effective difference between declaring a struct as

typedef struct {...} Foo;

and

struct Foo {...};

I know the second requires you to prefix uses with struct , but what are the differences between these two definitions that I'll notice when writing or executing the program? What about with enum s?

Answer 1

Update: please see comments attached to answer for clarification.

Original post.

Besides having to write "struct" everywhere , something else of note is that using a typedef will allow you to avoid subtle syntax errors when working with pointers :

Quote:

Typedefs can also simplify declarations for pointer types. Consider this:

struct Node {
    int data;
    struct Node *nextptr;
};

Using typedef, the above code can be rewritten like this:

typedef struct Node Node;
struct Node {
    int data;
    Node *nextptr;
};

In C, one can declare multiple variables of the same type in a single statement, even mixing pointer and non-pointers. However, one would need to prefix an asterisk to each variable to designate it as a pointer. In the following, a programmer might assume that errptr was indeed a Node *, but a typographical error means that errptr is a Node. This can lead to subtle syntax errors.

struct Node *startptr, *endptr, *curptr, *prevptr, errptr, *refptr;

By defining a Node * typedef, it is assured that all the variables will be pointer types.

typedef struct Node *NodePtr;
...
NodePtr startptr, endptr, curptr, prevptr, errptr, refptr;

Answer 2

If you write

typedef struct {...} foo;

It saves you from having to write struct foo everywhere: you can just write foo .

(You get this notational convenience for free in C++ by the way).

Answer 3

我会看一下这个问题 ，然后总结一下struct { ... }和typedef struct { ... }之间没有明显的功能差异，尽管如果正确使用后者可能会使你的代码变得更简单，更容易理解。